A typical surface acoustic wave (SAW) device functions as a filter or a resonator for a specific range of radio frequency (RF) inputs. When implemented in the appropriate feedback circuit configuration, the SAW resonator along with associated electronic circuitry functions as an oscillator. When used as a serial component, the SAW resonator functions as a simple filter. Such electronic circuitry is usually embodied on a circuit board and housed within an enclosure.
For high performance applications, the SAW device must be thermally stable to ensure stable RF performance. Typically, a heater element is physically coupled externally to the enclosure containing the SAW circuitry. In this way, the whole device package, supporting electronics and the SAW device within the package is heated and hence thermally stabilized. Alternatively, in some designs, one or more heater elements are physically coupled to a stiffener block attached to the back side of the circuit board to which one or more SAW devices are mounted in an attempt to apply heat more directly to the SAW device.
The result in the prior art is a large thermal resistance between the SAW device and the heater resulting in excessive losses with commensurate increased time and/or heater power necessary to achieve required thermal stability. Moreover, it may, in some instances, be undesirable to unnecessarily heat secondary electronic components associated with the SAW device as this incurs unnecessary reliability degradation. Also, due to the additional components associated with the heater and the cost of hybrid heater devices themselves, the cost of the final product in the prior art increases as does the difficulty of assembly.